How to create a stopwatch

Hey guys, I'm trying to do a GUI in which, when a button is pressed time starts to count. I created this code but when I push the button nothing happens. I think the problem is I have nested functions and they're not working. Can someone tell me the problem?

% --- Executes on button press in start.
function start_Callback(hObject, eventdata, handles)
% hObject    handle to start (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
c = now;
  function a
  a = timer('ExecutionMode','fixedRate','Period',1,'TimerFcn',@stopwatch);
  start(a)
  end
      function stopwatch(obj,evt)
      b = now;
      t = b - c;
      set(handles.text2,'string',datestr(t));
      end
end

Thank you!

Answer 1

[Walter Roberson]

The timerfcn should be given as @stopwatch

[Renato Pereira]

Still not working :(

[Walter Roberson]

The code

function a
a = timer('ExecutionMode','fixedRate','Period',1,'TimerFcn',@stopwatch);
start(a)
end

declares a function named 'a', and inside the function assigns a variable named 'a' a timer and starts the time, and then lets the timer go out of scope (which would delete the timer.) However, the rest of your code never calls the function 'a', so the timer is not created at all.

% --- Executes on button press in start.
function start_Callback(hObject, eventdata, handles)
  % hObject    handle to start (see GCBO)
  % eventdata  reserved - to be defined in a future version of MATLAB
  % handles    structure with handles and user data (see GUIDATA)
  c = now;
  a = timer('ExecutionMode','fixedRate','Period',1,'TimerFcn',@stopwatch);
  start(a)
  handles.a = a;
  guidata(hObject, handles);

    function stopwatch(obj,evt)
      b = now;
      t = b - c;
      set(handles.text2, 'string', datestr(t, 'HH:MM:SS'));
    end
  end